The present invention relates to a vehicle stabilizing device and a method according to the preamble of claim 1 and 13, respectively.
The basic ESP-strategy (Electronic Stability Program) for stabilizing a vehicle in the unbraked case relates to the specific deceleration of individual wheels by an active pressure buildup in the corresponding wheel brake cylinder. A stabilizing torque (yaw torque) is thereby imparted to the vehicle structure by decrease of lateral force and simultaneous increase in longitudinal force or brake force. In contrast to the unbraked case, an existing initial pressure distribution and, thus, force distribution on the wheels must be based on for the introduction of a stabilizing yaw torque, during simultaneous braking by the driver, the said distribution being caused by the driver""s initial pressure or, if necessary, by the pressure level introduced by the ABS (anti-lock system).
An object of the present invention is to provide a braking strategy which permits stabilizing a vehicle in the actively braked case with pressure increase so that an optimum is achieved that is made up of the driver""s wish to brake, the vehicle stabilization or steerability of the vehicle and the pedal and sound comfort.
This object is achieved in a generic device by the features of claim 1 and in a generic method by the features of claim 1* (*Translator""s note: claim xe2x80x9813xe2x80x99 is most likely referred to).
The provision of a vehicle stabilizing device for modifying brake pressures on wheels of a vehicle according to input data which performs a variation of the brake pressures on at least one wheel according to a way of influencing an intervention unit that provides a number of influencing cycles or influencing strategies, permits achieving a stabilization of the vehicle with an optimum possible deceleration as long as possible by means of the prevailing driver""s initial pressure without active pressure buildup beyond this pressure level, the above influencing being defined by the driver brake pressure.
The great advantage of the pressure modulations below the driver""s initial pressure is that they allow to be carried out in a way which is very comfortable for the driver. Thus, the separating valves (TCS 1/2) used in a vehicle stabilizing device (for example, as disclosed in DE 19816290) remain open in this condition range and the switch-over valves (SV 1/2) remain closed so that no pedal reactions will be caused and noise will not develop due to the intervention which might minimize the comfort of the driver.
In addition, the pressure increase requirement in the second influencing cycle is equal to the driver""s initial pressure so that, beside the separating and switch-over valve, also the inlet valve of the corresponding wheel remains permanently open, with the result of further improvement of the pedal comfort.
The present invention also relates to a vehicle stabilizing method for modifying brake pressures on wheels in a vehicle according to input data, wherein the brake pressures on at least one wheel are varied according to a way of influencing which is selected from several influencing cycles or influencing strategies, the said influencing being defined by the brake pressure effected by the driver.
Favorable embodiments of the present invention are indicated in the subclaims.
The present invention permits greatly improving the effectiveness of the intervention and the comfort compared to the previous intervention. More specifically, pressure reduction on the curve-outward wheel in the understeering case causes buildup of cornering forces which decisively improve the steerability of the vehicle and its stabilization. The simultaneous pressure increase on the curve-inward rear wheel allows limiting the reduced deceleration due to the pressure increase on the front wheel. Preventing the pressure increase beyond the driver""s initial pressure and, hence, circumventing the energization of the separating and switch-over valve, especially in the event of minor to medium vehicle instabilities, enhances comfort during the intervention.
This arrangement specifically focuses on the improvement of comfort in ESP interventions with medium and small vehicle instability by avoiding a pressure increase in excess of the driver""s initial pressure.